Caulking is to seal a certain structure where air, water, or noise may be leaked through a joint or a seam of the structure. Generally, a caulk tube or a caulk gun which cradles the caulk tube is used for the caulking. Such a caulk tube usually has a nozzle which is tapered from its base end to a point at its top end, but the taper dimension of the nozzle can vary depending on its manufacturer. The caulking could require a certain condition such as a certain taper dimension of the caulk tube's nozzle or a certain angle of the nozzle depending on a working environment. Thus, it would be beneficial for a user if the user can change the nozzle of the caulk tube as the user desires.